This invention relates to a new and improved trip-free operating mechanism for a load break switch and particularly to a switch operating mechanism readily adaptable to both manual and electrical tripping, including remote electrical tripping and remote closing.
Fused load break switches are frequently used in service entrance equipment and in other relatively high current applications; typically, multiple-pole switches of this kind may require interruption of currents of the order of 400 to 80,000 amperes. It is critically important that the contacts of these switches open and close rapidly to minimize arcing and thereby avoid pitting and deterioration of the switch contacts. The switches usually provide for latching of the switch contacts in the closed position. The switch blades are relatively heavy and the mechanical forces entailed in opening and closing operations are often substantial.
Other problems have been found in the use and operation of such heavy-duty switches. The forces needed to actuate the switch, both during opening and closing, are considerable because the opening and closing springs of typical operating mechanisms work against each other at times. The closing of the contacts of a switch requires rotation of the operating handle first through a limited arc in one direction and then through a greater arc in the opposite direction, thus complicating the switch closing process. In some operating mechanisms, the on-off condition of the switch contacts is indicated only by the position of the operating handle, causing uncertainty as to whether the operating mechanism is in its on, off or in its reset positions. Additional problems have arisen because the closing speed of the switch contacts is not completely independent of the speed of rotation of the operating handle. Further, the operating handle cannot be manipulated to break welds holding the switch contacts partially closed in the event the opening spring drive does not overcome the adhesions caused by such welds and leaves the contacts in an intermediate, hung-up position.